Posts Tagged ‘South Pacific’

The global ocean is made up of five major ocean basins: the Pacific, Atlantic, Indian, Southern and Arctic Ocean. The Pacific Ocean is the largest of these basins as well as the deepest. Its expanse runs 155 million square miles and contains “more than half of the free water on earth.” Not only is it the largest and deepest ocean basin, but it is also the oldest, comprised of rocks that have been dated to be 200 million years old. You may have heard the term “Ring of Fire” associated with the Pacific Ocean. This name stems from the fact that the Pacific Ocean is prone to earthquakes and formation of submarine volcanoes along its extensive ridge and trench systems.

Ring of Firehttp://oceanexplorer.noaa.gov/explorations/05fire/background/volcanism/media/tectonics_world_map.html

The Pacific Ocean gained its name in the 16th century from the Portuguese navigator Ferdinand Magellan. Magellan and his crew set sail from Spain in 1519 in search of the Spice Islands located to the northeast of Indonesia. The Spice Islands were the largest producers in the world of spices such as nutmeg, cloves, and pepper. They navigated through the Atlantic Ocean and around the tip of South America after which they came across an unfamiliar ocean. He called this ocean ‘pacific’ which means peaceful. Unbeknownst to them, they still had a long journey to the Spice Islands. You can learn more about the voyage of Magellan and his crew here.

OK, back to science! The CLIVAR P16S field campaign has entered the waters of the South Pacific known as a subtropical gyre. Gyre means “circular or spiral motion.” In the ocean, wind generated surface currents travel in a circular direction, either clockwise or counterclockwise, forming a large, circular body of water. The circular direction of the currents is caused by the Coriolis Force acting to deflect motion to the right in the Northern Hemisphere and to the left in the Southern Hemisphere due to the Earth’s rotation. The South Pacific gyre is located in the Southern Hemisphere, so winds and water are deflected to the left. Because of the deflection to the left, the gyre circulates in the counterclockwise direction, forcing water to pile up in the center of the gyre. In the last post, “An Appreciation for True-Color Satellite Imagery” we discussed how microscopic plants, or phytoplankton, require nutrients to grow. Blooms (large cell numbers) of phytoplankton cannot grow in these gyres because the water that piles up within the center of circulation is nutrient deficient.

We can use the information about the color of the light being absorbed and reflected by the ocean to deduce the concentration of phytoplankton biomass using the proxy Chlorophyll a. Chlorophyll a is a pigment that both land plants and phytoplankton use to convert light to sugars in their chloroplast. Chlorophyll a absorbs strongly in the blue color of light. So when there is a lot of Chlorophyll a, then the light reflected back includes very little blue light. When there is very little or no Chlorophyll a, then a lot of blue light is reflected back. The figure below is an ocean color image based on the information I just described. The blue color represents little to no Chlorophyll a (or phytoplankton) present while the bright colors of yellow green and red represent increasing concentration of Chlorophyll a or phytoplankton biomass.

Please bear in mind that this explanation is very simplistic. You can learn more about how ocean color works here.

See the image below for the current cruise track of CLIVAR P16S. They are almost in Tahiti. Just a couple more weeks…

Cruise Track, CLIVAR-P16S

ACKNOWLEDGEMENTS: NASA’s Ocean Ecology Laboratory Field Support Group is participating in the US Repeat Hydrography, P16S field campaign under the auspices of the International Global Ocean Ship-Based Hydrographic Investigations Program (GO-SHIP). The US Climate Variability and Predictability Program (CLIVAR), NOAA and the NSF sponsor this campaign.

One of the greatest tools used by oceanographers today for measuring ocean processes is the CTD. CTD stands for Conductivity, Temperature and Depth. Conductivity is a measure of ocean salinity. The CTD is used to collect profile data in the ocean. The CTD is typically accompanied by a carousel, or rosette, of large bottles (Niskins) that can hold about 10 liters (2.6 U.S. gallons) of water. Some Niskins are large enough to hold 30 liters. These bottles have spring-loaded caps that can be triggered to close at specified depths. The CTD and other sensors, such as a chlorophyll fluorometer, and an Acoustic Doppler Current Profiler (ADCP) that measures current velocities, and other sensors can also be attached within the rosette package.

The whole package is connected to a very long cable and is mechanically lowered by a winch operator down through the water column, which is called the ‘downcast.’ During the downcast, information about salinity, temperature, depth and data from the other sensors are sent to a computer on board the ship. The computer is connected through the cable that is lowering the package. The downcast is halted once the package reaches close to the ocean floor. When the CTD is raised back to the surface, the ‘upcast’, each of the Niskin bottles is closed at assigned depths, collecting water as it travels back to the surface.

Once the Rosette package is back aboard the ship, the scientists are able to collect water from the bottles for their analyses. The parameters collected and analyzed during CLIVAR campaigns includes but are not limited to: salinity, oxygen, nutrients, chlorofluorocarbons (CFCs), dissolved inorganic carbon (DIC), total alkalinity, pH, dissolved organic carbon (DOC), helium, and tritium.

Certain compounds, such as some radionuclide (tritium, carbon-14, etc.) and CFCs, can be used as ‘tracers’. These tracers are used to follow ocean currents and calculate the age of water parcels. CFCs were prominently used in refrigerators and air conditioning units until the 1970s when they were banned over the concern of ozone depletion. You can learn more about the CFC tracer program here. Through the WOCE and CLIVAR programs CFC concentrations have been measured all over the world.

Map of global CFC measurementshttp://www.pmel.noaa.gov/cfc/

The measurement of pH, total alkalinity and DIC are important for monitoring ocean acidification. Ocean acidification (OA) is the decrease in ocean pH as a result of an increase in carbon dioxide (CO2) absorption by seawater. OA is a prominent concern in today’s world. CO2 is pumped into the atmosphere from everyday human activities, such as emissions from vehicles and industrial pollution. Each year approximately 25% of the CO2 pumped into the atmosphere is absorbed by the ocean. Although plants can use CO2 for photosynthesis, the increase also has negative implications. As the amount of CO2 absorbed by the increases, the pH is expected to continue decreasing.

pH time serieshttp://www.pmel.noaa.gov/co2/story/OA+Observations+and+Data

The pH of the ocean directly affects organisms that form calcium carbonate shells or structures, like corals, oysters, clams and sea urchins. An acidic environment causes the calcium carbonate to dissolve and makes it more difficult for the organisms to make their calcium carbonate skeletons. Therefore, it is important that programs like CLIVAR are monitoring global CO2 concentrations (part of the DIC pool), total alkalinity (the ability for the ocean to neutralize acids) and pH. We know that decreases in ocean pH can negatively impact marine organisms. You can see more about the effect of ocean acidification or marine organisms here.

As I was conducting some research for this blog post I came across this article that was posted at the Earth Observatory in 2008 about the global carbon budget. I thought it was appropriate to bring it back here.

ACKNOWLEDGEMENTS: NASA’s Ocean Ecology Laboratory Field Support Group is participating in the US Repeat Hydrography, P16S field campaign under the auspices of the International Global Ocean Ship-Based Hydrographic Investigations Program (GO-SHIP). The US Climate Variability and Predictability Program (CLIVAR), NOAA and the NSF sponsor this campaign.

Three members of the Ocean Ecology Laboratory’s Field Support Group (FSG; Code 616) will embark on a 45-day journey from Hobart, Tasmania to Papeete, Tahiti on the icebreaker R/V Nathaniel B. Palmer (NBP). The field campaign is part of the US Repeat Hydrography, P16S, 2014 under the auspices of GO-SHIP and sponsored by the US Climate Variability and Predictability Program (CLIVAR). You can find more information about the program here. The FSG will collect biogeochemical samples and bio-optical data across the South Pacific. These data will eventually be ingested into NASA’s SeaWiFS Bio-optical Archive and Storage System (SeaBASS) and subsequently used for ocean color satellite validation activities.

During the next six weeks, I will be helping my colleagues chronicle their journey over the high seas. They will share not only information about the science but also describe the daily life of a sea-going scientist. I, too, participate in many of these campaigns and am very familiar with the NBP having sailed on it three times during my career. Alas, I could not participate in the journey so must live vicariously through my colleagues. Below, you will find the biographies of the three NASA scientists that are participating on this cruise: Joaquin Chaves, Scott Freeman, and Mike Novak. You can also follow the ship track here.

Joaquin Chaves, received his PhD in oceanography from the University of Rhode Island in 2004. For his graduate work he conducted research on estuarine biogeochemistry. He held postdoctoral positions at the Marine Biological Laboratory in Woods Hole, MA, and at Brown University, in RI, where he focused on the biogeochemistry of land use change in tropical forests, particularly in the Amazon region. He’s been a contract scientist at NASA-GSFC since 2009, where he has focused on ocean color satellite remote sensing and marine bio-optics. He has participated in ocean-going field campaigns to the Atlantic, Pacific, and Arctic Oceans, as well as the East China Sea.

Joaquin Chaves

A native Californian, Scott Freeman grew up in Salinas, near the Monterey Bay, and attended the University of California, San Diego. After a lengthy hiatus in New York City, he returned to college and received a B.S. in Biology from the City University of New York. He then attended the University of Rhode Island’s Graduate School of Oceanography, completed a master’s degree, and stayed in Rhode Island to work first for the URI, and then for Wetlabs, a manufacturer of oceanographic optical instruments. While in Rhode Island, he participated in many cruises and coastal exercises, including NASA’s Southern Ocean Gas Exchange Experiment (SO GASEX) and ONR’s Radiance in a Dynamic Ocean experiments (RADYO).

Since joining SSAI in 2011, Scott has participated in several field campaigns for NASA’s Ocean Ecology Laboratory, and is responsible for AOP and IOP data collection and processing. He lives in Alexandria, VA with his wife Heidi and sons Charles and Adrian. When not engaged in field research, one can find him playing bass for the Washington Metropolitan Philharmonic Orchestra.

Scott Freeman

Mike Novak grew up in Piscataway, New Jersey, about 30 miles southwest of Newark. After graduating high school he attended the Richard Stockton College of New Jersey where he earned a B.S. degree in marine science. After college, he attended graduate school at the University of New Hampshire where he earned an M.S. degree in Oceanography. He worked as a researcher at UNH before relocating to the Washington D.C. area where he now works as an oceanographic researcher at NASA-GSFC. When he is not sailing the high seas, he is also an avid musician playing at various venues around the D.C. area with his band Novakaine.